The shape of feature code: an analysis of twenty C-preprocessor-based systems

Feature annotations (e.g., code fragments guarded by #ifdef C-preprocessor directives) control code extensions related to features. Feature annotations have long been said to be undesirable. When maintaining features that control many annotations, there is a high risk of ripple effects. Also, excessive use of feature annotations leads to code clutter, hinder program comprehension and harden maintenance. To prevent such problems, developers should monitor the use of feature annotations, for example, by setting acceptable thresholds. Interestingly, little is known about how to extract thresholds in practice, and which values are representative for feature-related metrics. To address this issue, we analyze the statistical distribution of three feature-related metrics collected from a corpus of 20 well-known and long-lived C-preprocessor-based systems from different domains. We consider three metrics: scattering degree of feature constants, tangling degree of feature expressions, and nesting depth of preprocessor annotations. Our findings show that feature scattering is highly skewed; in 14 systems (70 %), the scattering distributions match a power law, making averages and standard deviations unreliable limits. Regarding tangling and nesting, the values tend to follow a uniform distribution; although outliers exist, they have little impact on the mean, suggesting that central statistics measures are reliable thresholds for tangling and nesting. Following our findings, we then propose thresholds from our benchmark data, as a basis for further investigations.     

Comparison of instantaneous reactive power <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">q</Emphasis> theory with theory of the current's physical components

The comparison of the instantaneous reactive power (IRP) p-q theory with the theory of the current's physical components (CPC) presented in this paper provides the relationship between powers in both theories applied to three-phase, three-wire circuits with sinusoidal voltages and currents. It shows that results of the instantaneous reactive power p-q theory are inconsistent with power phenomena in such circuits. Namely, the IRP q may occur in circuits with linear, purely resistive loads thus, with zero reactive power, Q, and the instantaneous active power p may occur in circuits with purely reactive loads, thus, with zero active power, P. Consequently, the IRP p-q theory fails to identify the power properties of three-phase circuits with unbalanced loads. Moreover, in spite of sinusoidal supply and the lack of distortion, the IRP p-q theory suggests that the active and reactive currents contain a third-order harmonic. Also the IRP p-q theory is not capable of providing information on power properties of the load instantaneously.     

Referenzprozessabläufe für Telekommunikationsunternehmen

The telecommunication market is experiencing substantial changes. New business models, innovative services, and technologies require reengineering, transformation, and process standardization. Enterprise Architecture Frameworks support the transformation by specifying methods, procedures, and reference models. With the Enhanced Telecom Operation Map (eTOM), the TM Forum offers an international de facto reference process framework, based on specific features and requirements of the telecommunication industry. However, this reference framework only offers a hierarchical collection of processes on different levels of abstraction; a control view in terms of a sequential ordering of tasks and hence a real process flow as well as an end-to-end view on the customer are missing. In this paper, we extend the eTOM reference model by reference process flows, in which we abstract and generalize the knowledge about processes in telecommunication companies. With reference process flows, we aim to assist companies in achieving a structured and transparent re-structuring and re-design of their processes. We demonstrate the applicability and usefulness of our reference process flows in two case studies, and evaluate them by means of criteria for reference model evaluation. Our reference process flows have been accepted as a standard by the TM Forum and published as part of eTOM version 9. We further elaborate on those components of our approach which can be applied outside the telecommunication industry.     

Failure of Emergency Batteries for Aircrafts due to Stress-Corrosion Cracking

Several electrical brass (CuZn37) connector bolts of aircraft batteries failed as a result of stress-corrosion cracking. The batteries are used for emergency supply of the avionics in case of power failure or for complete control in the case of engine failure. For activation, the thermal battery is heated by a pyrotechnic element and then supplies electrical power with 5 A for 20 min up to 240 A for 3 min. For assembly of the batteries, an acetic acid curing silicone resin is used for housing seal on the lid and on the connector bolts. Because of the almost hermetic sealing of the enclosure, the silicone resin cures very slowly and metallic parts are exposed to the acetic acid vapor. So the electrical brass connector showed corrosive attack with the formation of copper acetate (verdigris). Subsequent failure due to stress-corrosion cracking occurred. The failure type and damage mechanisms could be simulated in laboratory experiments.     

Spontaneous intracranial hypotension: report of four cases and review of the literature

Spontaneous intracranial hypotension is an unusual syndrome of postural headache and low cerebrospinal fluid pressure without an established cause. We present four cases, analyze those previously reported in the literature, examine the MRI, CT, angiographic and cisternographic finding and discuss the clinical picture, proposed pathophysiologic mechanisms and potential treatment.     

Isolation,characterization, and quantitative analysis of Microviridin J,a new Microcystis metabolite toxic to Daphnia

This paper describes the purification and characterization of microviridin J, a newly discovered metabolite of Microcystis that causes a lethal molting disruption in Daphnia spp., upon ingestion of living cyanobacterial cells. Microviridin J consists of an acetylated chain of 13 amino acids arranged in three rings and two side chains. Unlike other known isoforms of microviridin, microviridin J contains arginine that imparts a unique solution conformation characterized by proximal hydrophobic interactions between Arg and other regions of the molecule. This eventually results in the formation and stabilization of an additional ring system. Microviridin J potently inhibits porcine trypsin, bovine chymotrypsin, and daphnid trypsin-like proteases. The activity against trypsin is most likely due to Arg and its distinctive conformational interactions. Overall, the data presented for microviridin J emphasize once again the ability of cyanobacteria to produce numerous and potent environmental toxins.